Gap Junction Channels Play an Essential Role in Irradiation-Induced Bystander Effect on Human Fibroblast Cell

Our previous study showed that nitric oxide was involved in the irradiation-induced multiplies bystander effects of increasing cell proliferation and enhancing cell plating efficiency but inducing micronucleus production. In the present work, with a confluent human fibroblast cell population, the chemical factor and its transfer pathway involved in irradiation-induced bystander effect were investigated. Micronucleus (MN) and G1-phase arrest could be detected in the cells irradiated by carbon ion beam. It was found that a low dose irradiation had a high effectiveness in producing MN, which indicated an existence of bystander effect. This low dose sensitive was enhanced by the treatment of 8-Br-cAMP that increased gap junctional intercellular communication (GJIC), and it was effectively reduced by the treatment of 5% DMSO. No low dose sensitive was observed when the cells were treated by 100 mM lindane, an inhibitor of GJIC. In addition, the irradiation-induced G1-phase arrest was also enhanced by cAMP but was obviously reduced by DMSO or lindane. Again, the role in alleviating irradiation-induced G1-phase arrest of lindane was greater than that of DMSO. A microbeam device was also used for this study. It was found that even 1 cell in a confluence AG1522 cell population was irradiated by exact one Ar13+ (~1200 keV/mm) or Ne7+ (~430 keV/mm) particle, additional MN could be detected in hundreds of other unirradiated cells. In addition, the yield of MN increased with the number of irradiated cells. But there was no significant difference in the MN induction when the cells were irradiated by the particles with different numbers. The MN induction was partly reduced by the treatment of cells with DMSO, and was much effectively eliminated by the treatment of lindane. Our results obtained from both random irradiation and precise numbered irradiation indicate that both GJIC and reactive oxygen species (ROS) contributed to the irradiation-induced bystander effect, but the cell gap junction channels likely play an essential role in the release and transfer of irradiation-induced chemical factors and than mediate the bystander effect in dominative.The 3rd National Meeting of Ion Beam Bioengneering and The 1st International Symposium on Ion Beam: Biological Effects and Molecular Mechanism